Solution processable fluorene-extended Indeno[1,2-b]anthracenes: Synthesis, characterization and photophysical properties

Efficient fluorescent emitters indenoanthracenes (indene-fused anthracenes) were conjugatively extended by a fluorene unit to achieve larger molecular size derivatives of this semiconductor class. These new fluorene-extended indenoanthracene derivatives were prepared in two steps from the corresponding indenoanthraquinones in good overall yields (56–71%). They showed good solubility in common organic solvents and intense fluorescence. The synthesis and photophysical, thermal and electroluminescence properties of compounds are described. The photophysical properties of indenoanthracenes were examined by UV-vis and fluorescence spectroscopies. The indenoanthracenes in solution and thin film were found to emit in the range of 480–520 nm with good quantum yields (Φ_ƒ, 0.51–0.71). They also exhibited relatively high initial decomposition temperatures varying from 330 to 390 °C. The fluorene–extended indenoanthracenes were used as an emissive layer for the fabrication of solution-processed OLEDs. Using the device with the structure of ITO/PEDOT:PSS/indenoanthracene–D/BCP/Alq₃/LiF/Al; a maximum luminous efficiency of 1.74 cd/A was obtained with an external quantum efficiency (EQE) of 0.73%.